Did anybody heard about this, that people couldn't repent before the Flood? Here is the excerpt from the book Seven Gates of Righteous Knowledge (published by AskNoah International, 2017, authors: Rabbi Moshe Weiner and Dr. Michael Schulman): "Also, humanity will never become that wicked again, and people have ability to repent, which they did not have before the Flood". Source for this was Sefer HaSichot.
Cain could repent and he lived before the Flood. HaShem told him that.
Anybody have some idea about this?